WATER, a transparent fluid, without co lour, smell, or taste, in a very small degree compressible ; when pure, not liable to spontaneous change ; liquid in the com mon temperature of our atmosphere, as suming the solid form at 32° Fahrenheit, and the gaieous at 212°, but returning unaltered to its liquid state on resuming any degree of heat between these points; capable of dissolving a greater number of natural bodies than any other fluid what ever, especially of those known by the name of the saline ; performing the most important functions in the vegetable and animal kingdoms, and entering largely into their composition as a constituent part. Water is formed of hydrogen, combined with oxygen, in the proportion of 14.42 to 85.58. Water is assumed as the standard, or unity, in all tables of spe cific gravity. A cubic inch of it weighs, at thirty inches of the barometer, and 60° thermometer, 252,422 grains. Water does not enter the list of materia medics of any of the colleges ; but it is so impor tant, both as an article of diet, and as an agent in the cure of diseases, that a brief account of its varieties and properties cannot but be proper in this place. The purest natural water is melted snow, or rain, collected in the open fields. That which falls in towns, or is collected from the roofs of houses, is contaminated with soot, animal effluvia, and other impuri ties ; although, after it has rained for some time, the quantity of these diminishes so much, that Morveau says, it may be ren dered almost perfectly pure by means of a little barytic water, and exposure to the atmosphere. Rain water, after it ails, either, remains on the surface of the earth, or penetrates through it until it meets with some impenetrable obstruc tion to its progress, when it bursts out at some lower pale, forming a spring or well. The water on the surface of the earth either descends along its declivities in streams, which, gradually wearing channels fur themselves, combine to form rivers, which at last reach the sea ; or it remains stagnant in cavities of considera ble depth, forming lakes or ponds, or on nearly level ground, forming marshes. Although the varieties of spring waters are exceedingly numerous, they may be divided into, 1. The soft, which are suf ficiently pure to dissolve soap, and to an swer the purposes of pure water in gene ral. 2. The hard, which contain earthy salts, decompose soap, and are unfit for many purposes, hall in domestic econo my and manufactures. 3. The saline, which are strongly impregnated with soluble salts. When spring waters pos sess any peculiar character, they are called mineral waters. See WATERS, mineral.
River water is in general soft, as it is formed of spring water, which, by expo sure becomes more pure ; and running surface water, which, although turbid from particles of clay suspended in it, is otherwise very pure. Lake water is similar to river water. The water of marshes, on the contrary, is exceedingly impure, and often highly fetid, from the great propor tion of animal and vegetable matters con stantly decaying in them.
So early as the year 1776, an experi ment was made by ;.lacquer to ascertain what would be the product ef the combus tion of inflammable air, or hydrogen gas. He accordingly set fire to a bottle full of it, and held a saucer over the flame, but no soot appeared upon it as he expect ed, for it remained quite clean, and was bedewed with drops which were found to be pure water. Various conjectures were now formed about the nature of the pro duct of the combustion of oxygen and hy drogen gases. By some it was supposed the carbonic acid gas ; by others it was conjectured it would be the sulphurous or sulphuric acid. The latter was the opinion of 1L Lavoisier. Such were the experiments and opinions of the French chemists previously to the year 1781. About the beginning of that year, Mr. Waritire, a lecturer in natural philosophy, had long entertained an opinion that the combustion of hydrogen gas with atmo spheric air, might determine the question, whether heat be a heavy body. Appre hensive of danger in making the experi ment, he bad tor some time declined it, but was at last encouraged by Dr. Priest ley, and accordingly prepared an appara tus for the purpose. This was a copper vessel properly fitted, and filled with at mospherical air and hydrogen gas, which was exploded by making the electric spark pass through it. A loss of weight of two grains was observed after the com bustion. A similar experiment was re peated in close glass vessels, which, though clean and dry before the combus tion, became immediately wet with mois ture, and lined with a sooty matter. This sooty matter, Dr. Priestley afterwards supposed, proceeded from the mercury which had been employed in filling the vessel. During the same year Mr. Ca vendish repeated the experiments of Mr. Warltire and Dr. Priestley. He perform ed them several times with atmospheric air and hydrogen gas, in a vessel which held 24,000 grains of water, and be never could perceive a loss of weight more than one•fifth of a grain, and often none at all.
In all these experiments not the least sooty matter appeared in the inside of the glass. To examine the nature of the dew which appeared in the inside of the glass, he burnt 500,000 grain measures of hy drogen gas, with about two and a half times that quantity of common air ; and in this combustion he obtained one hundred and thirty-five grains of water, which had neither taste nor smell, and when it was evaporated, left no sensible sediment: It seemed to be pure water. In another experiment, he exploded, in a glass globe, 19,500 grain measures of oxygen gas, and 37,000 of hydrogen gas, by means of the electric spark. The result of the experiment was thirty grains of water, which contained a small quantity of nitric acid. The experiments of Mr. Cavendish were made in the year 1781, and they are undoubtedly conclusive with regard to the composition of water. It would appear that Mr. Watt entertained the same ideas on this subject., When he was informed by Dr. Priestley of the result of these experiments, he observes, "Let us consider what obviously happens in the deflagration of hydrogen and oxy gen gases. These two kinds of air unite with violence, they become red hot, and when cooling totally disappear. When the vessel is cooled, a quantity of water is found in it equal to the weight of the air employed. The water is then the only remaining product of the process ; and water, light, and heat, are all the products, unless there be some other matter set free, which escapes our senses. . Are we not then authorised to conclude, that water is composed of oxygen and hydrogen gases, deprived of part of their latent or elementary heat ; that oxygen gas is composed of water, deprived of its hydrogen, and united to elementary heat and light ; and that the latter are contained in it in a latent state, so as not to be sensible to the thermometer or to the eye ? And if light be only a modifi cation of heat, or a circumstance attend ing it, or a component part of the hy drogen gas, then oxygen gas is compos ed of water deprived of its hydrogen, and united to elementary heat." Thus it appears that Mr. Watt had a just view _ of the composition of water, and of the nature of the process by which its com ponent parts pass to a liquid state from that of an elastic fluid. Towards the end of the same year, M. Lavoisier had made some experiments, the result of whick surprised him ; for the product of the combustion of the oxygen and hydrogen gases, instead of being sulphuric or sul- • phurous acid, as he expected it, was pure water. This led him to procure an ap- , paratus, with which the experiment might be performed on a large scale, and with more accuracy and precision. Ac. cordingli the experiments were perform ed on the twenty-fourth of June, 1783, in presence of several academicians, and also of Sir Charles Illagclen, who was at that time in Paris. A similar experiment was afterwards performed by M. Monge, with the same result ; and it was repeat ed again by Lavoisier and Meusnier, on a scale so large as to put the matter beyond a doubt. The conclusion, therefore, from the whole was, that water is corn posed of oxygen and hydrogen. Water calks in three different states ; in the solid state, or state of ice, in the liquid, and in the state of vapour or steam. Its principal properties have already been detailed, in treating of the effects of calo ric. It assumes the solid form when it is cooled down to the temperature of 32°. • In this state it increases in bulk, by which it exerts a prodigious expansive force, , which is owing to the new arrangement of its particles, which assume a crystal line form, the crystals crossing each other at angles of 60° or 120°. The specific gravity of ice is less than that of water. When ice is exposed to a temperature above 32°, it absorbs caloric, which then becomes latent, and is converted into the liquid state, or that of water. At the temperature of 42 V, water has reached its maximum of density. According to the experiments of Lefevre Gineaux, a French cubic foot of distilled water, taken at its maximum of density, is equal to 70 pounds, 223 grains French, equal 529,452.9492 troy grains. An English cubic foot at the same temperature weighs 437,102.4946 grains troy. By Professor Robinson's experiments it is ascertained, that a cubic foot of water, at the tempe rature of 55°, weighs 998.74 avoirdupois ounces, of 437.5 grains troy each, or about 1* ounce less than 1000 avoirdu pois ounces. When water is exposed to the temperature of 212°, it boils ; and if this temperature be continued, the whole is converted into an elastic invisi ble fluid, called vapour or steam. This, as has been already shown, is owing to the absorption of a quantity of caloric, which is necessary to retain it in the fluid form. In this state it is about 1800 times its bulk when in the state of water. This shows what an expansive force it must exert when it is confined, and hence its application in the steam engine, of which it is the moving power.